Extension-ladder.



No. 678,549. Patented July l6, 190l.

W. N. DERBY.

EXTENSION LADDER.

(Application filed Apr. 17. 1801.) (No Model.) 2 Sheets-Sheet l.

RS co. vnmoumo No. 678.549. Patented July I6, l90l.

W. N. DERBY.

EXTENSION LADDER.

(Application filed Apr. 17, 1901.) (No Model.) 2 Sheets-8heat 2.

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citizen of the United UNITED STATES PATENT rrion.

WALTER N. DERBY, OF ETNA, NEW HAMPSHIRE.

EXTENSION-LADDER.

SPECIFICATION forming part of Letters Patent N 0. 678,549, dated July 16, 19011 Application filed April 17, 1901. Serial No. 56,336. (No model.)

To aZZ'whom it may concern.-

Be it known that I, WALTER N. DERBY, a States of America, and a resident of Etna, county of Grafton, State of New Hampshire,have invented certain new and useful Improvements in Extension-Ladders, of which the following is a specification.

My invention relates to an improvement in extension-ladders, and has for its object to provide a ladder which can be raised and lowered and held at different altitudes, which is very simple, inexpensive, and durable in construction and easy to operate, and is animprovement on my Patent No. 326,205, dated September 15, 1885.

My invention consists in the features and combination of features, as hereinafter more fully described and claimed.

In the drawings, Figure l is a front View in elevation; Fig. 2, acentral vertical section; Fig. 3, a detail view of the locking-lever; Fig. 4, a detail view of the trippingdog; Fig. 5, a section, on an enlarged scale, of a portion of the two sections of the ladder, showing the locking-lever and tripping-dog; Fig. 6, a sectional view showing the bearing-plates of the locking-lever and tripping-dog; and Figs. 7 and 8, top plan and sectional views, respectively, of the bearing-plate of the lockinglever.

Referring to the drawings, in which like letters of reference denote like parts throughout the several views, A represents the lower or main section of the ladder, having side pieces B and rungs G, and D is the upper slidable section, having side pieces E and rungs F. Gand H are clamps secured to the 7 side pieces B and E, respectively, which hold i said sections together.

I is a plate secured to the inner surface of the lower or main section B, between two of the rungs thereof.

K is a' hollow post projecting from the rear of the plate I and seatedin a recess K in the section B, and L is a hollow post, and M a stop-pin,both projecting from the front of said plate.

N is a locking-lever mounted on the post L, provided at one end with a curved recess 0 and at the opposite end with a projection or toe P and a stop-shoulder Q.

R is a spring, one end secured to the side piece of the ladder and the other end engaging the locking-lever and adapted to hold the lever in a position to be engaged by the rungs of the slidable section of the ladder.

S is a screw-bolt which passes through the side piece of the ladder and the posts of the plate I for the purpose of securing the locking-lever in place.

T is a plate secured to the inner surface of the lower or main section B of the ladder, just below the plate I, and provided with a hollow post T, projecting from the rear thereof and seated in a recess T in section B, and a hollow post T projecting from the front thereof.

U is a tripping-dog mounted on post T and provided with a rounded under surface U and a rounded head V and a notch V at one end and the opposite end weighted and provided with a beveled end, as at V.

V is a screw-bolt which passes through the side piece of the ladder and the posts of the plate T for the purpose of securing the trip ping-dog in place.

W is a pulley secured to the inner face of the side of the lower section of the ladder, and X is a rope which is passed over the pul ley W and both free ends of which are at tached to the lower rung of the upper slidable section, making the rope a long loop, so that said section may be raised by hand.

It will be noticed that the upper slidable section is away from the person and the rope at one side, so as to be out of the wa The locking-lever is prevented from moving outward past the rungs of the slidable section by the stop -shoulder on the same abutting against the stop-pin on the plate I. The rungs of the slidable section are spaced, so that when the two sections of the ladder are locked together the recess in the end of the locking-lever will be in engagement with a rung of said sliding section, and at the same time the tripping-dog will rest on the next rung below, and when the slidable section is slid downward the rungs of the same will come in contact one at a time with the beveled end of the tripping-dog and cause said dog to move the locking-lever outward a sufficient distance to allow the upper end of the lever to clear the said rungs.

I have described the locking-lever, tripping-dog, &c., as applied to only, one side of the lower or main section of the ladder; but they may be applied with equal facility to both sides. Instead of having two separate supporting-plates for the locking-lever and tripping-dog they may both be mounted on the same plate.

I do not wish to be limited to the precise construction as herein shown and described,- and the same may be varied somewhat withv out departing from the spirit of my invention. The operation is as follows: The slidable section of the ladder being slid upward by means of the rope or any other suitable means, the locking-lever and tripping-dog will pass the rungs of the same, and when it is desired to lock the ladder at a certain rung the locking-lever is stopped at a position just below said rung, leaving the tripping-dog resting on the next rung below. Said slidable section is then slid slightly downward until the curved recess at the end of the locking-lever engagestherung. VVhenitisdesiredtolower the slidable section, it is raised, so that the end of the locking-lever is in a position about midway between the rung it has been engaged with and the next rung below, and the tripping-dog is below any rung of said section. The said slidable section is then slid downward, and'as each rung comes in contact with the beveled end of the tripping-clog it will slide down the same, move the said dog, and cause the head of the same to engage the projection of the locking-lever, which in turn causes said lever to move outward against the action of the spring sufticiently to clear the rungs of the slidable section. It will be seen that when the slidable section is slid upward the rungs thereof will retract the locking-lever against the action of the spring; but when said section is slid downward the trippingdog will retractthe locking-lever as each rung passes the dog.

' I claim is- 1, An extension-ladder comprising a slidable section, a stationary section provided with a pivoted locking-lever having a recess at one end adapted to engage the rungs of the slidable section, and a toe at the opposite end, a tripping-dog engaging said too, the tripping-dog being operated by the slidable section and said locking-lever operated by the tripping-dog, substantially as described.

2. An extension-ladder comprising a lower or main section provided with a stop-pin, a pivoted locking-lever having a recess at one end and a projection at the opposite end, a shoulder to abut against the stop-pin, and a tripping-dog engaging said projection, an upper slidable section having rungs which engage the recess in the end of the locking-1ever and lock the upper sliding section to the lower section, and also engage the tripping- Having thus described my invention, what dog to release said sliding section, substantially as described. v

3. An extension-ladder comprising a stationary section provided with a pivoted locking-lever having a recess at one end, and a projection at theopposite end, a spring bearing on said lever, a tripping-dog having a notch at one end with which said projection engages and the'ogposite end beveled, and a slidable section adapted to engage the beveled end of the tripping-dog and the recess of the lockinglever, substantially as described.

4. An extension-ladder comprising a slidable section, a stationary section provided with a stop=pin, a spring-pressed pivoted locking-lever having a recess at one end to engage the rungs of the slidable section, a projection at the opposite end, and a stop-shoul= der on the edge to abut against said stop-pin, a spring, and a tripping-dog with a rounded head at one end adapted to engage said projection, and its opposite end beveled and adapted tobe engaged by the rungs of the slidable section, substantially as described.

5. An extension-ladder comprising an upper slidable section, a lower section provided with a plate having a stop-pin, and hollow posts, one of said posts seated in a recess in the side of the section and the other post having a spring-pressed locking-lever thereon provided with a shoulder to engage the stoppin, and a tripping-dog for operating said locking-lever adapted to be operated by the rungs of the slidable section, substantially as described.

6. An extension-ladder comprising an upper slidable section, a lower section provided with a spring-pressed locking-lever, and a weighted tripping-dog one end beveled and adapted to be engaged by the rungs of the slidable section when the same is slid downward, the opposite end engaging the said locking-lever, the lower edge rounded and adapted to be engaged by the rungs of the slidable section when the same is slid upward, substantially as described.

7. An extension-ladder comprising an upper slidable section, a lower section having plates with hollow posts extending from the front and rear thereof, the rear posts seated in recesses in the side of the lower section, one of said plates provided with a springpressed lever pivoted on its front post and having a shoulder, a stop-pin, with which said shoulder engages, and a tripping-dog pivoted on the front post of the other plate adapted to be operated by the rungs of the slidable section and move the locking-lever outward, substantially as described.

Signed by me, at Lebanon, New Hampshire, this 30th day of March, 1901.

WALTER N. DERBY. Witnesses:

F. W. LAKEMAN, M. O. CAMP. 

